How to export chart from excel to image using C#

Hi,

Am a new user. If am posting in a wrong forum am sorry and please suggest me where I can get my problem solved.
The problem am facing is,
Am having 6 charts in an excel worksheet and am trying to export all the charts from excel to some jpeg file.
Only two charts getting exported and remaining charts after I export as Image, its empty (0 kb). I can see only empty jpeg file.
Am using C# and Asp.Net. The code what am using is,

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Please give me some suggestion to export all the 6 charts from excel.
I searched in most of the forum but I didnt get the required answer.
Please help me out in sorting the issue.
Urgent Please.